Effects of hypercapnia on cochlear and cerebral blood flow in rabbits

Cochlear blood flow (CoBF) and cerebral blood flow (CBF) were measured using laser Doppler flowmetry and the microsphere method during CO2 and O2 gas mixture inhalation in rabbits. Both methods revealed that CBF was increased by CO2 inhalation. CoBF measured by laser Doppler measurement decreased during CO2 inhalation while that measured by the microsphere method showed a slight increase, but lateral wall blood flow in the cochlea measured by the microsphere method showed no significant change. Our results obtained with laser Doppler flowmetry were not inconsistent with those reported in humans. It is considered that the rabbit, in which thick bone surrounds the cochlea, is a good model for the experimental evaluation of the laser Doppler technique used in the clinical measurement of CoBF.